1. Field of the Invention
The present invention relates to an apparatus and a method for testing belt tension of a belt drive for a product such as a washing machine or the like, and more particularly to an apparatus and a method for automatically testing initial belt tension of the belt drive on an assembly line.
2. Description of the Prior Art
In general, a belt drive transmits power using frictional forces between a belt and belt pulleys. The frictional forces are caused by a belt tension of the belt drive, and the initial belt tension is generated when the length of the belt is a little shorter than the theoretically geometrical length thereof. The belt tension of the belt needs to be controlled to be an appropriate value. That is, in case the initial belt tension is too small, sliding is generated between the belt and the belt pulleys and the power cannot be effectively transmitted between the belt and the belt pulleys. On the other hand, in case the belt tension is too large. excessive loads are exerted to a drive motor. Therefore, the belt tension of the belt drive is conventionally controlled to be a predetermined value in which loads and torques needed in a product to which the belt drive are mounted is considered.
FIG. 1 schematically shows a conventional belt drive of a washing machine. Referring to FIG. 1, in the belt drive, a motor 2 and a reduction gear 3 are fixed to a bracket 1 and are spaced apart from each other. Pulleys 4 and 5 are respectively mounted in surrounded to shafts of the motor 2 and the reduction gear 3, and a belt 6 is wound around the pulleys 4 and 5. An initial belt tension of belt drive is controlled by moving the motor 2 and thus regulating the distance between the motor 2 and the reduction gear 3. The belt drive is mounted on a bottom surface of a washing tub (not shown) upside-down, and the initial belt tension is controlled before the washing machine is assembled.
In order to test the belt tension, as indicated by arrows of FIG. 1, the belt 6 is pressed on both sides by a force, and the displacements d of the belt 6 at the pressed positions are measured by a scale.
However, in the conventional method for testing an initial belt tension of a belt drive, the testing result may depend on pressed positions and directions of the belt and also skillfulness of testing workers, which impair the reliability of the test. As a result, belt tensions of belt drives are occasionally re-controlled after products are completely assembled.
On the other hand, it is preferable to automate assembly lines of a product to increase the productivity thereof. Especially in a washing machine, the belt drive bracket assembly line and the washing tub assembly line for mounting the bracket to the washing tub need to be inlined, and therefore the belt tension should be tested on the assembly line.
However, as above-described, the conventional belt tension testing method, due to its manual characteristics, has been an obstacle to automation of an assembly line, deteriorating productivity of a product.